Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$71.31	12.783%	$80.4256	$80.43	$80.45	$80.40
Purchase #2	$230.92	4.760%	$241.9118	$241.91	$241.90	$241.90
Purchase #3	$63.65	5.377%	$67.0725	$67.07	$67.05	$67.10
Purchase #4	$168.39	6.591%	$179.4886	$179.49	$179.50	$179.50
Purchase #5	$71.41	6.422%	$75.996	$76.00	$76.00	$76.00
Purchase #6	$235.60	11.123%	$261.8058	$261.81	$261.80	$261.80
Purchase #7	$166.89	7.525%	$179.4485	$179.45	$179.45	$179.40
7 purchase totals =	$1,008.17		$1,086.1488	$1,086.16	$1,086.15	$1,086.10